1. Field of the Invention
The present invention relates to sodium styrenesulfonate hemihydrate, a composition containing the sodium styrenesulfonate hemihydrate, and processes for production thereof.
More specifically, the present invention relates to sodium styrenesulfonate hemihydrate which is a novel styrenesulfonate compound having excellent stability with less polymerization liability, and less lumping liability, a composition containing it, and a process for production thereof.
2. Description of the Related Art
Sodium styrenesulfonate is well known to be produced from an aqueous .beta.-haloethylbenzenesulfonate solution by reaction with an aqueous sodium hydroxide solution.
For example, JP-B-53-23292 discloses a method in which an aqueous .beta.-haloethylbenzenesulfonic acid solution is added dropwise to an alcoholic solution of sodium hydroxide to allow the reaction to proceed at 50-70.degree. C.; JP-A-52-23038 discloses a method in which an aqueous .beta.-haloethylbenzenesulfonic acid solution is added dropwise to 35 wt % sodium hydroxide solution in a nitrogen atmosphere at a temperature of 95-105.degree. C. to allow the reaction proceed to cause crystallization of the product; and J-PB-38-20570 discloses a two-step reaction method in which an aqueous .beta.-haloethylbenzenesulfonic acid solution is added to an aqueous sodium hydroxide solution at room temperature or a lower temperature to produce once sodium salt of .beta.-haloethylbenzenesulfonic acid, then the solution is heated to 80-100.degree. C., and an aqueous sodium hydroxide solution is added thereto to obtain sodium styrenesulfonate in a crystal state.
Sodium styrenesulfonate produced by the above methods is used practically as a dyeing assistant, a surfactant, a viscosity-reducing agent, and so forth.
The sodium styrenesulfonate produced by any of the above conventional methods, however, is less stable in storage and transportation, and can polymerize in a degree of 10% or more by weight in several months to cause decrease of the effective component content, or can cause lumping by bridging between the particles, disadvantageously.
As a countermeasure against the polymerization, a polymerization inhibitor, such as a nitrite salt, hydroquinone, and hydroquinone monomethyl ether, is added after the synthesis and/or solid-liquid separation of the sodium styrenesulfonate, whereby the polymerization is retarded remarkably, and the product is produced and marketed commercially. However, the polymerization inhibition is not sufficient yet, and the large amount of the added polymerization inhibitor poses another problem of drop of the reactivity of the sodium styrenesulfonate. As the countermeasure against the lumping, the conditions of storage and transportation are carefully controlled without a special measure. In some cases, granulation is tried. However, the above countermeasures are not substantially effective.